Display device, method of manufacturing the same, and electronic apparatus

ABSTRACT

There is provided a display device including: a light emitting element; and a drive transistor (DRTr) that includes a coupling section (W1) and a plurality of channel sections (CH) coupled in series through the coupling section (W1), wherein the drive transistor (DRTr) is configured to supply a drive current to the light emitting element.

CROSS REFERENCES TO RELATED APPLICATIONS

The present Application is a Continuation Application of applicationSer. No. 16/369,162, filed Mar. 28, 2019 which is a continuationApplication of Ser. No. 16/296,612, filed Mar. 8, 2019, which is aContinuation Application of application Ser. No. 16/181,838, filed Nov.6, 2018 which is a Continuation Application of application Ser. No.16/014,753, filed Jun. 21, 2018, and issued as U.S. Pat. No. 10,147,779,Dec. 4, 2018, which is a Continuation Application of U.S. patentapplication Ser. No. 15/965,153, filed Apr. 27, 2018 and issued as U.S.Pat. No. 10,121,841 on Nov. 6, 2018, which is a Continuation Applicationof U.S. patent application Ser. No. 15/813,983, filed Nov. 15, 2017 andissued as U.S. Pat. No. 10,026,796 on Jul. 17, 2018, which is aContinuation Application of U.S. patent application Ser. No. 14/909,586,filed Feb. 2, 2016 and issued as U.S. Pat. No. 10,103,212 on Oct. 16,2018, which is a 371 National Stage Entry of International ApplicationNo.: PCT/JP2014/068876, filed on Jul. 16, 2014, which in turn claims thebenefit of priority of the Japanese Patent Application No. 2013-189836,filed on Sep. 12, 2013, and the Japanese Patent Application No.2014-021604, filed on Feb. 6, 2014, both filed with the Japan PatentOffice, the entire contents of these applications are incorporatedherein by reference.

TECHNICAL FIELD

The present disclosure relates to a display device including acurrent-driven display element, a method of manufacturing such a displaydevice, and an electronic apparatus provided with such a display device.

BACKGROUND ART

In recent years, in a field of display devices performing image display,a display device (an organic electro luminescence (EL) display device)using a current-driven optical element as a light emitting element, thelight emission luminance of which is varied based on a value of aflowing current, such as an organic EL element, has been developed andcommercialization thereof is progressing. Unlike a liquid crystalelement or other element, the light emitting element is a selflight-emitting element, and a separate light source (a backlight) is notrequired. Therefore, the organic EL display device has characteristicsof high visibility of an image, low power consumption, and high responsespeed of the element, and the like, as compared with a liquid crystaldisplay device which requires a light source.

In such a display device, a unit pixel may include, for example, a writetransistor and a drive transistor. The write transistor is adapted toselect a unit pixel in which a pixel signal is to be written, and thedrive transistor is adapted to supply a current to a light emittingelement. For example, in PTL 1, there is disclosed a display device inwhich a current driving capability of the drive transistor is set lowerthan a current driving capability of the write transistor. Further, forexample, in PTL 2, there is disclosed a display device in which achannel length L of the drive transistor is set larger than a channellength L of the write transistor. Further, for example, in PTL 3, thereis disclosed a display device further including an AC transistor, and aratio (L/W) of a channel length L to a channel width W of the drivetransistor is set larger than a ratio (L/W) of a channel length L to achannel width W of the AC transistor.

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No.2003-308030

PTL 2: Japanese Unexamined Patent Application Publication No. 2008-46427

PTL 3: Japanese Unexamined Patent Application Publication No.2005-202371

SUMMARY

Incidentally, in the display device, high image quality is typicallydesired, and further improvement in image quality is expected.

Therefore, it is desirable to provide a display device, a method ofmanufacturing the display device, and an electronic apparatus that makeit possible to enhance image quality.

An display device according to an embodiment of the disclosure includesa light emitting element and a drive transistor. The drive transistorincludes a coupling section and a plurality of channel sections coupledin series through the coupling section. The drive transistor isconfigured to supply a drive current to the light emitting element.

A method of manufacturing a display device according to an embodiment ofthe disclosure includes: forming a drive transistor and a writetransistor, the drive transistor including a coupling section and aplurality of channel sections coupled in series through the couplingsection, and the write transistor configured to transfer a pixel voltageto a gate electrode of the drive transistor; and forming a lightemitting element supplied with a current by the drive transistor.

An electronic apparatus according to an embodiment of the disclosure isprovided with the foregoing display device, and non-limiting examples ofthe electronic apparatuses may include a television, a digital camera, apersonal computer, a video camera, and a mobile terminal device such asa mobile phone.

In the display device, the method of manufacturing the display device,and the electronic apparatus according to the respective embodiments ofthe disclosure, the light emitting element is supplied with the drivecurrent from the drive transistor. The drive transistor includes thecoupling section and the plurality of channel sections that are coupledin series through the coupling section.

According to the display device, the method of manufacturing the displaydevice, and the electronic apparatus of the respective embodiments ofthe disclosure, the drive transistor including the coupling section andthe plurality of channel sections coupled in series through the couplingsection is used, which makes it possible to enhance image quality.Moreover, effects described here are non-limiting. Effects achieved bythe technology may be one or more of effects described in the presentdisclosure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration example of adisplay device according to a first embodiment of the disclosure.

FIG. 2 is a circuit diagram illustrating a configuration example of asub-pixel illustrated in FIG. 1.

FIG. 3 is a cross-sectional view illustrating a schematic sectionalstructure of a display section illustrated in FIG. 1.

FIG. 4A is a schematic diagram illustrating a structure example of apixel illustrated in FIG. 1.

FIG. 4B is another schematic diagram illustrating the structure exampleof the pixel illustrated in FIG. 1.

FIG. 4C is a schematic diagram illustrating another structure example ofthe pixel illustrated in FIG. 1.

FIG. 5 is an explanatory diagram illustrating a configuration example ofa circuit region.

FIG. 6 is a plan view illustrating a configuration example of a drivetransistor illustrated in FIG. 2.

FIG. 7 is a timing waveform chart illustrating an operation example ofthe display device illustrated in FIG. 1.

FIG. 8 is an explanatory diagram for explaining scanning by an ELAapparatus.

FIG. 9A is an explanatory diagram illustrating an example of a directionof the drive transistor illustrated in FIG. 2.

FIG. 9B is an explanatory diagram illustrating another example of thedirection of the drive transistor illustrated in FIG. 2.

FIG. 10 is a plan view illustrating a configuration example of a drivetransistor according to a modification of the first embodiment.

FIG. 11 is a plan view illustrating a configuration example of a drivetransistor according to another modification of the first embodiment.

FIG. 12A is a schematic cross-sectional view illustrating a structureexample of a drive transistor according to another modification of thefirst embodiment.

FIG. 12B is a schematic cross-sectional view illustrating a structureexample of a drive transistor according to still another modification ofthe first embodiment.

FIG. 12C is a schematic cross-sectional view illustrating a structureexample of a drive transistor according to still another modification ofthe first embodiment.

FIG. 13 is an explanatory diagram illustrating a structure example of acircuit region according to another modification of the firstembodiment.

FIG. 14 is a plan view illustrating a configuration example of a drivetransistor in the circuit region illustrated in FIG. 13.

FIG. 15 is a schematic diagram illustrating a structure example of apixel according to still another modification of the first embodiment.

FIG. 16A is a schematic diagram illustrating a structure example of apixel according to still another modification of the first embodiment.

FIG. 16B is another schematic diagram illustrating the structure exampleof the pixel illustrated in FIG. 16A.

FIG. 17A is a schematic diagram illustrating a structure example of apixel according to still another modification of the first embodiment.

FIG. 17B is another schematic diagram illustrating the structure exampleof the pixel illustrated in FIG. 17A.

FIG. 18A is a schematic diagram illustrating a structure example of apixel according to still another modification of the first embodiment.

FIG. 18B is a schematic diagram illustrating a structure example of apixel according to still another modification of the first embodiment.

FIG. 18C is a schematic diagram illustrating a structure example of apixel according to still another modification of the first embodiment.

FIG. 18D is another schematic diagram illustrating the structure exampleof the pixel illustrated in any of FIGS. 18A to 18C.

FIG. 19A is a schematic diagram illustrating a structure example of apixel according to still another modification of the first embodiment.

FIG. 19B is a schematic diagram illustrating a structure example of apixel according to still another modification of the first embodiment.

FIG. 19C is a schematic diagram illustrating a structure example of thepixel illustrated in any of FIGS. 19A and 19B.

FIG. 20A is a plan view illustrating a configuration example of a drivetransistor according to another modification of the first embodiment.

FIG. 20B is a plan view illustrating a configuration example of a drivetransistor according to still another modification of the firstembodiment.

FIG. 21 is a sectional diagram illustrating schematic sectionalstructures of respective transistors according to a second embodiment.

FIG. 22 is an explanatory diagram illustrating a process ofmanufacturing the transistors illustrated in FIG. 21.

FIG. 23 is a sectional diagram illustrating schematic sectionalstructures of respective transistors according to a modification of thesecond embodiment.

FIG. 24 is an explanatory diagram illustrating a process ofmanufacturing the transistors illustrated in FIG. 23.

FIG. 25 is a sectional diagram illustrating schematic sectionalstructures of transistors according to a modification of the secondembodiment.

FIG. 26 is an explanatory diagram illustrating a process ofmanufacturing the transistors illustrated in FIG. 25.

FIG. 27 is a sectional diagram illustrating schematic sectionalstructures of respective transistors according to a modification of thesecond embodiment.

FIG. 28 is an explanatory diagram illustrating a process ofmanufacturing the transistors illustrated in FIG. 27.

FIG. 29 is an explanatory diagram illustrating grains of a transistoraccording to a third embodiment.

FIG. 30 is a schematic diagram illustrating an implementation example ofa display device according to the third embodiment.

FIG. 31 is a sectional diagram illustrating schematic sectionalstructures of respective transistors according to a modification of thethird embodiment.

FIG. 32 is a plan view illustrating a configuration example of the drivetransistor illustrated in FIG. 31.

FIG. 33 is a plan view illustrating a configuration example of a drivetransistor according to another modification of the third embodiment.

FIG. 34 is a perspective view illustrating an appearance configurationof a television to which the display device according to any of theembodiments is applied.

FIG. 35 is a circuit diagram illustrating a configuration example of asub-pixel according to a modification.

FIG. 36 is a timing waveform chart illustrating an operation example ofa display device including the sub-pixel illustrated in FIG. 35.

FIG. 37 is a circuit diagram illustrating a configuration example of asub-pixel according to another modification.

FIG. 38A is a plan view illustrating a configuration example of a drivetransistor according to a reference example.

FIG. 38B is a plan view illustrating a configuration example of a drivetransistor according to another reference example.

FIG. 38C is a plan view illustrating a configuration example of a drivetransistor according to still another reference example.

FIG. 38D is a plan view illustrating a configuration example of a drivetransistor according to still another reference example.

MODE FOR CARRYING OUT THE INVENTION

Some embodiments of the disclosure are described in detail below withreference to drawings. Moreover, description thereof is given in thefollowing order.

-   1. First embodiment-   2. Second embodiment-   3. Third embodiment-   4. Application examples

1. First Embodiment Configuration Example

FIG. 1 illustrates a configuration example of a display device accordingto first embodiment. A display device 1 may be an active matrix displaydevice using an organic EL element. Moreover, a display driving methodand a method of manufacturing the display device according to respectiveembodiments of the disclosure are implemented by the present embodiment,and the description thereof is therefore given together.

The display device 1 may include a display section 10 and a drivesection 20. The drive section 20 may include a picture signal processingsection 21, a timing generation section 22, a scan line drive section23, a power line drive section 26, and a data line drive section 27.

The display section 10 may be configured of a plurality of pixels Pixthat are arranged in a matrix. Each of the pixels Pix may include foursub-pixels 11 (11R, 11G, 11B, and 11W) of red (R), green (G), blue (B),and white (W). In this example, the four sub-pixels 11R, 11G, 11B, and11W may be arranged in two rows and two columns in each of the pixelsPix. More specifically, in each of the pixels Pix, the red (R) sub-pixel11R may be disposed on upper left, the green (G) sub-pixel 11G may bedisposed on upper right, the blue (B) sub-pixel 11B may be disposed onlower left, and the white (W) sub-pixel 11W may be disposed on lowerright.

FIG. 2 illustrates an example of a circuit configuration of thesub-pixel 11. The display section 10 may include a plurality of scanlines WSL and a plurality of power lines PL that extend in the rowdirection, and a plurality of data lines DTL extending in a columndirection. Although not illustrated, one end of each of the data linesDTL may be coupled to the data line drive section 27, one end of each ofthe scan lines WSL may be coupled to the scan line drive section 23, andone end of each of the power lines PL may be coupled to the power linedrive section 26. Each of the sub-pixels 11 may be disposed at anintersection between each of the scan lines WSL and each of the powerlines DTL.

The sub-pixel 11 may include a write transistor WSTr, a drive transistorDRTr, a light emitting element 30, and a capacitor Cs. In other words,in this example, the sub-pixel 11 may have a so-called “2Tr1C”configuration that is configured of two transistors (the writetransistor WSTr and the drive transistor DRTr) and one capacitor Cs.

The write transistor WSTr and the drive transistor DRTr may be eachconfigured of, for example, an N-channel metal oxide semiconductor (MOS)thin film transistor (TFT). A gate of the write transistor WSTr may becoupled to the scan line WSL, a source thereof may be coupled to thedata line DTL, and a drain thereof may be coupled to a gate of the drivetransistor DRTr and one end of the capacitor Cs. The gate of the drivetransistor DRTr may be coupled to the drain of the write transistor WSTrand the one end of the capacitor Cs, a drain thereof may be coupled tothe power line PL, and a source thereof may be coupled to the other endof the capacitor Cs and an anode of the light emitting element 30.

The one end of the capacitor Cs may be coupled to, for example, the gateof the drive transistor DRTr, and the other end thereof may be coupledto, for example, the source of the drive transistor DRTr. The lightemitting element 30 may be a light emitting element configured of anorganic EL element, and the anode thereof may be coupled to the sourceof the drive transistor DRTr and the other end of the capacitor Cs, anda cathode thereof may be supplied with a voltage Vcath that is adirect-current voltage by the drive section 20. The light emittingelement 30 may emit white light. More specifically, in this example, aswill be described later, the sub-pixels 11R, 11G, 11B, and 11W maygenerate light of red (R), green (G), blue (B), and white (W),respectively, with use of the light emitting element 30 emitting whitelight and a color filter 218 (described later).

FIG. 3 is a sectional diagram of the display section 10. The displaysection 10 may include a transparent substrate 200, a gate 201, apolysilicon 203, an anode 212, a light emitting layer 230, a cathode216, and the color filter 218.

The transparent substrate 200 may be a support substrate of the displaysection 10, which may be formed of, for example, glass or plastic.Further, although the transparent substrate 200 is used in this example;alternatively, a non-transparent substrate such as a metal plate may beused. The gate 201 may be selectively formed on the transparentsubstrate 200. The gate 201 may be formed of, for example, molybdenum(Mo). An insulating layer 202 may be provided on the transparentsubstrate 200 and the gate 201. The insulating layer 202 may be formedof, for example, silicon oxide (SiO2) or silicon nitride (SiNx). Thepolysilicon 203 may be so provided on the insulating layer 202 as tocover a region corresponding to the gate 201. The gate 201 and thepolysilicon 203 may configure a drive transistor DRTr and any otherdevices. Moreover, in this example, the transistor has a so-calledbottom gate structure in which the gate 201 is formed below thepolysilicon 203; however, the structure of the transistor is not limitedthereto. The transistor may have a so-called top-gate structure in whicha gate is formed above a polysilicon. An insulating layer 204 may beprovided on the polysilicon 203 and the insulating layer 202. Theinsulating layer 204 may be formed of a material similar to that of theinsulating layer 202, for example. Further, a contact/wiring 205 may beso provided in a portion of the region where the polysilicon 203 isprovided as to penetrate the insulating layer 204. The wiring 205 may beconfigured of three layers of, for example, titanium (Ti)/aluminum(Al)/titanium (Ti).

An insulating layer 211 may be provided on the insulating layer 204. Theinsulating layer 211 may be formed of, for example, polyimide or acrylicresin. An anode 212 may be selectively formed on the insulating layer211. The anode 212 may penetrate the insulating layer 211 to be coupledto the contact/wiring 205 relating to the source of the drive transistorDRTr. The anode 212 may be formed of, for example, ITO/Al alloy, Alalloy, ITO/Ag alloy, or ITO/Ag alloy. In other words, the anode 212 maydesirably have property to reflect light. An insulating layer 213 may beprovided on the anode 212 and the insulating layer 211. The insulatinglayer 213 may be formed of a material similar to that of the insulatinglayer 211, for example. An opening WIN may be provided at a portion ofthe region where the anode 212 is formed in the insulating layer 213.The light emitting layer 230 configured of a yellow light emitting layer214 and a blue light emitting layer 215 may be uniformly provided abovethe anode 212 and the insulating layer 213. The yellow light emittinglayer 214 may be an organic EL layer emitting yellow (Y) light, and maybe formed of a material emitting yellow light. The blue light emittinglayer 215 may be an organic EL layer emitting blue (B) light, and may beformed of a material emitting blue light. Moreover, in this example, theblue light emitting layer 215 is laminated on the yellow light emittinglayer 214; however, the structure is not limited thereto. Alternatively,for example, the yellow light emitting layer 214 may be laminated on theblue light emitting layer 215. The cathode 216 may be uniformly providedon the blue light emitting layer 215. The cathode 216 may be atransparent or semitransparent electrode, and may be formed of, forexample, magnesium silver (MgAg) or IZO (registered trademark). In thecase where the cathode 216 is formed of magnesium silver, the cathode216 with the thickness of about several nm may be made semi-transparent.In the case where the cathode 216 is formed of IZO, it is desirable toform the cathode 216 to have a film thickness in a range from severaltens nm to several thousand nm, for example. In other words, IZO is atransparent material, this allows for formation of the cathode 216 witha slightly large thickness to achieve a desired low sheet resistancevalue. An insulating layer 217 may be provided on the cathode 216. Theinsulating layer 217 may be formed of, for example, silicon nitride(SiNx). The insulating layer 217 may be provided to prevent change ofcharacteristics such as light emission efficiency that is caused bymoisture entering the light emitting layer 230. Moreover, when issuescaused by entering of moisture are resolved by any other technology, theinsulating layer 217 may be omitted. A transparent substrate 220 may bebonded to the insulating layer 217 with the insulating layer 221 that isa sealing resin in between. The transparent substrate 220 may have thecolor filter 218 and a black matrix 219 formed on a surface thereof. Thetransparent substrate 220 may be formed of a substrate havingtransparency because the transparent substrate 220 is provided on asurface from which light is emitted as will be described later. A red(R) color filter 218 may be disposed in a region corresponding to thesub-pixel 11R, a green (R) color filter 218 may be disposed in a regioncorresponding to the sub-pixel 11G, a blue (B) color filter 218 may bedisposed in a region corresponding to the sub-pixel 11B, and a white (W)color filter 218 may be disposed in a region corresponding to thesub-pixel 11W.

FIG. 4A schematically illustrates a structure of the pixel Pix, and FIG.4B schematically illustrates a sectional structure of the pixel Pix.Thus, in the pixel Pix, yellow light emitted from the yellow lightemitting layer 214 and blue light emitted from the blue light emittinglayer 215 may be mixed to become white light, and the white light maytravel in a direction opposite to the transparent substrate 200 servingas the support substrate. In other words, the light emitting element 30may be a so-called top-emission light emitting element. The white lightmay be then outputted from a display surface through the color filter218. More specifically, in the sub-pixels 11R, 11G, and 11B, a redcomponent, a green component, and a blue component may be separated fromthe white light and outputted by the color filters 218 of red (R), green(G), and blue (B), respectively. Further, in the sub-pixel 11W, colorgamut of the white light may be adjusted by the white (W) color filter218. Moreover, for example, in an application in which desired imagequality (color gamut) is not so high, the white (W) color filter 218 maynot be provided.

Further, in this example, the yellow light emitting layer 214 is formedof a material emitting yellow (Y) light; however, the material is notlimited thereto. Alternatively, for example, as illustrated in FIG. 4C,the yellow light emitting layer 214 may be configured of a materialemitting red (R) light doped with a material emitting green (G) light,or a material emitting green (G) light doped with a material emittingred (R) light. Even in this case, the lamination order of the lightemitting layers may be changed.

FIG. 5 illustrates arrangement of the anode 212 in the pixel Pix. In thepixel Pix, four circuit regions 15R, 15G, 15B, and 15W and four anodes212R, 212G, 212B, and 212W may be provided.

The circuit region 15R may be a region where devices (the writetransistor WSTr, the drive transistor DRTr, and the capacitor Cs) otherthan the light emitting element 30 in the sub-pixel 11R are provided.Likewise, the circuit region 15G may be a region where devices otherthan the light emitting element 30 in the sub-pixel 11G are provided.The circuit region 15B may be a region where the devices other than thelight emitting element 30 in the sub-pixel 11B are provided. The circuitregion 15W may be a region where the devices other than the lightemitting element 30 in the sub-pixel 11W are provided. In each of thecircuit regions 15R, 15G, 15B, and 15W, the write transistor WSTr, thedrive transistor DRTr, and the capacitor Cs may be arranged in the samelayout. Diverting the same layout in such a way makes it possible toenhance efficiency of layout process.

The anode 212R may be the anode 212 of the sub-pixel 11R, the anode 212Gmay be the anode 212 of the sub-pixel 11G, the anode 212B may be theanode 212 of the sub-pixel 11B, and the anode 212W may be the anode 212of the sub-pixel 11W. The anodes 212R, 212G, 212B, and 212W may berespectively coupled to the sources of the drive transistors DRTr formedin the circuit regions 15R, 15G, 15B, and 15W through the contact 205.

FIG. 6 illustrates a configuration example of the drive transistor DRTr.The polysilicon 203 of the drive transistor DRTr may be so formed as tobe overlapped with the gate 201 three times by being folded in a regionwhere the gate 201 is not provided. A folded portion W1 of thepolysilicon 203 may be injected with ions in manufacturing and may thusbe low in resistance. In other words, the portion, of the polysilicon203, overlapped with the gate 201 may function as an effective channelCH. Accordingly, three channels CH coupled in series may be juxtaposedin a direction intersecting the extending direction of the channels CHin the drive transistor DRTr. Also, as will be described later, in thedisplay device 1, all of the drive transistors DRTr in the displaysection 10 may be provided to allow the channels CH to extend in thesame direction. Such a configuration makes it possible to effectivelyutilize limited space to configure the drive transistor DRTr with longchannel length L, thereby enhancing image quality as will be describedlater.

As illustrated in FIG. 1, the drive section 20 may drive the displaysection 10, based on a picture signal Sdisp and a synchronization signalSsync that are supplied from outside. The drive section 20 may includethe picture signal processing section 21, the timing generation section22, the scan line drive section 23, the power line drive section 26, andthe data line drive section 27.

The picture signal processing section 21 may perform predeterminedsignal processing on the picture signal Sdisp supplied from the outsideto generate a picture signal Sdisp2. Examples of the predeterminedsignal processing may include gamma correction and overdrive correction.

The timing generation section 22 may be a circuit that supplies acontrol signal to each of the scan line drive section 23, the power linedrive section 26, and the data line drive section 27, based on thesynchronization signal Ssync supplied from the outside, to control thesesections to operate in synchronization with one another.

The scan line drive section 23 may sequentially apply a scan signal WSto the plurality of scan lines WSL according to the control signalsupplied from the timing generation section 22, to sequentially selectthe sub-pixels 11.

The power line drive section 26 may sequentially apply a power signal DSto the plurality of power lines PL according to the control signalsupplied from the timing generation section 22, to control lightemission operation and light extinction operation of the sub-pixels 11.The power signal DS may transit between a voltage Vccp and a voltageVini. As will be described later, the voltage Vini may be a voltage toinitialize the sub-pixels 11, and the voltage Vccp may be a voltage toallow a current Ids to flow through the drive transistor DRTr, therebycausing the light emitting element 30 to emit light.

The data line drive section 27 may generate a signal Sig according tothe picture signal Sdisp2 supplied from the picture signal processingsection 21 and the control signal supplied from the timing generationsection 22, and may apply the signal Sig to each of the data lines DTL.The signal Sig may include a pixel voltage Vsig that instructs emissionluminance of each sub-pixel 11.

As will be described later, this configuration allows the drive section20 to write the pixel voltage Vsig in each of the sub-pixels 11 andallows the light emitting element 30 to emit light with luminancecorresponding to the written pixel voltage Vsig, during one horizontalperiod.

Here, the channel CH corresponds to a specific but non-limiting exampleof “channel section” in the disclosure. The folded portion W1corresponds to a specific but non-limiting example of “coupling section”in the disclosure.

Operation and Action

Next, operation and action of the display device 1 according to thepresent embodiment is described.

Overall Operation Outline

First, with reference to FIG. 1, overall operation outline of thedisplay device 1 is described. The picture signal processing section 21may perform the predetermined signal processing on the picture signalSdisp supplied from the outside to generate the picture signal Sdisp2.The timing generation section 22 may supply the control signal to eachof the scan line drive section 23, the power line drive section 26, andthe data line drive section 27, based on the synchronization signal Ssync supplied from the outside, to control these sections to operate insynchronization with one another. The scan line drive section 23 maysequentially apply the scan signal WS to the plurality of scan lines WSLaccording to the control signal supplied from the timing generationsection 22 to sequentially select the sub-pixels 11. The power linedrive section 26 may sequentially apply the power signal DS to theplurality of power lines PL according to the control signal suppliedfrom the timing generation section 22, to control light emissionoperation and light extinction operation of the sub-pixels 11. The dataline drive section 27 may generate the signal Sig including the pixelvoltage Vsig that corresponds to luminance of each of the sub-pixels 11according to the picture signal Sdisp2 supplied from the picture signalprocessing section 21 and the control signal supplied from the timinggeneration section 22, and may apply the signal Sig to each of the datalines DTL. The display section 10 may perform display operation based onthe scan signal WS, the power signal DS, and the signal Sig that aresupplied from the drive section 20.

Detailed Operation

Next, detailed operation of the display device 1 is described.

FIG. 7 is a timing chart indicating the display operation of the displaydevice 1, where (A) illustrates a waveform of the scan signal WS, (B)illustrates a waveform of the power signal DS, (C) illustrates awaveform of the signal Sig, (D) illustrates a waveform of a gate voltageVg of the drive transistor DRTr, and (E) illustrates a waveform of asource voltage Vs of the drive transistor DRTr.

The drive section 20 writes the pixel voltage Vsig in each of thesub-pixels 11 during one horizontal period (1H) (writing period P1).Thereafter, the light emitting element 30 of each of the sub-pixels 11emits light with luminance corresponding to the written pixel voltageVsig (emission period P2). The detail thereof is described below.

First, the drive section 20 writes the pixel voltage Vsig in each of thesub-pixels 11 during a period from timing t1 to timing t2 (the wiringperiod P1). More specifically, first, the data line drive section 27sets the signal Sig to the pixel voltage Vsig at timing t1 ((C) of FIG.7), and the scan line drive section 23 changes the voltage of the scansignal WS from low level to high level ((A) of FIG. 7). This puts thewrite transistor WSTr into ON state, and the gate voltage Vg of thedrive transistor DRTr is accordingly set to the voltage Vsig ((D) ofFIG. 7). Further, at the same time, the power line drive section 26changes the power signal DS from the voltage Vccp to the the voltageVini ((B) of FIG. 7). This puts the drive transistor DRTr into ON state,and the source voltage Vs of the drive transistor DRTr is set to thevoltage Vini ((E) of FIG. 7).

Then, the scan line drive section 23 changes the voltage of the scansignal WS from high level to low level at timing t2 ((A) of FIG. 7).This puts the write transistor WSTr into OFF state, and the gate of thedrive transistor DRTr becomes floating. Thereafter, an inter-terminalvoltage of the capacitor Cs, namely, the gate-source voltage Vgs of thedrive transistor DRTr is maintained.

Next, the drive section 20 causes the sub-pixels 11 to emit light duringa period subsequent to timing t3 (the emission period P2). Morespecifically, at timing t3, the power line drive section 26 changes thepower signal DS from the voltage Vini to the voltage Vccp ((B) of FIG.7). This enables the current Ids to flow through the drive transistorDRTr, and the source voltage Vs of the drive transistor DRTr isaccordingly increased ((E) of FIG. 7). Along with the increase of thesource voltage Vs, the gate voltage Vg of the drive transistor DRTr isalso increased ((D) of FIG. 7). Then, when the source voltage Vs of thedrive transistor DRTr becomes larger than a sum (Vel+Vcath) of thethreshold voltage Vel of the light emitting element 30 and the voltageVcath, a current flows between the anode and the cathode of the lightemitting element 30, which results in light emission of the lightemitting element 30. In other words, the source voltage Vs is increasedby the amount corresponding to element variation of the light emittingelement 30, and the light emitting element 30 emits light.

Thereafter, in the display device 1, the period shifts from the emissionperiod P2 to the writing period P1 after the predetermined period (oneframe period) is elapsed. The drive section 20 performs driving torepeat the series of operation.

Image Quality

Next, the image quality of the display device 1 is described. The dataline drive section 27 may generate the signal Sig including the pixelvoltage Vsig that instructs emission luminance of each sub-pixel 11according to the picture signal Sdisp2 or any other signals, to applythe signal Sig to each of the data lines DTL. At this time, the pixelvoltage Vsig may be varied for each data line DTL due to characteristicvariation of the element in manufacturing the display device 1. Even inthis case, as illustrated in FIG. 7, in the display device 1, the drivetransistor DRTr is configured by coupling the plurality of channels CHin series, which makes it possible to reduce the risk of degradation inimage quality. The detail thereof is described below.

As illustrated in FIG. 7, in the sub-pixel 11, the gate voltage Vg ofthe drive transistor DRTr may be set to the pixel voltage Vsig and thesource voltage Vs may be set to the predetermined voltage Vini duringthe writing period P1. Then, the gate-source voltage Vgs (=Vsig−Vini) atthis time may be maintained during the emission period P2, and the drivetransistor DRTr may allow the drain current Ids corresponding to thegate-source voltage Vgs to flow through the light emitting element 30during the emission period P2. At this occasion, the drive transistorDRTr may operate in a so-called saturated region. The drain current Idsof the drive transistor DRTr in the saturated region may be generallyrepresented by the following expression.

$\begin{matrix}{{Ids} = {\frac{1}{2}\frac{W}{L}{{Cox} \cdot {\mu\left( {{Vgs} - {Vth}} \right)}^{2}}}} & \left\lbrack {{Expression}\mspace{14mu} 1} \right\rbrack\end{matrix}$

where W is a channel width, L is a channel length, Cox is a gateinsulating film capacity per unit area, μ is a mobility, and Vth is athreshold. The light emitting element 30 may then emit light withluminance corresponding to the drain current Ids.

Therefore, when the pixel voltage Vsig is varied for each data line DTL,the drain current Ids may be varied, and the luminance of the sub-pixel11 may be varied for each column of the sub-pixels 11. This may cause,for example, in the display image, a stripe extending in the columndirection of the sub-pixels 11, which may result in degradation in imagequality.

In the display device 1, since the plurality of channels CH are coupledin series to configure the drive transistor DRTr, it is possible toeffectively utilize limited space to achieve the drive transistor DRTrwith long channel length L. This allows for reduction of risk ofdegradation in image quality. In other words, for example, in the casewhere the drive transistor DRTr is configured of one channel CH, it isdifficult to achieve the drive transistor DRTr with long channel lengthL because the channel length of the drive transistor DRTr is restrictedby the area of the circuit regions 15R, 15G, 15B, and 15W. Inparticular, in the case where the drive transistor DRTr and the variouslines such as the data lines DTL, the scan lines WSL, and the powerlines PL are formed in the same layer, the channel length of the drivetransistor DRTr is further restricted by these lines, which results inshort channel length L. In contrast, in the display device 1 accordingto the present embodiment, since the drive transistor DRTr is configuredby coupling the plurality of channels CH in series, it is possible toeffectively utilize limited space to achieve the drive transistor DRTrwith long channel length L. This makes it possible to lower sensitivityof the gate-source voltage Vgs with respect to the drain current Ids inthe drive transistor DRTr, as illustrated in the expression (1).Accordingly, it is possible to suppress variation in the drain currentIds even if the pixel voltage Vsig is varied for each data line DTL,which makes it possible to suppress variation of the luminance of thesub-pixels 11 for each column. As a result, it is possible to reduce therisk that a stripe extending in the column direction of the sub-pixels11 occurs, for example, in the display image, which makes it possible toreduce the risk of degradation in image quality.

Also, since the channel length L of the drive transistor DRTr is madelong in this way, it is possible to suppress characteristic variation ofthe drive transistor DRTr itself. This makes it possible to suppressdegradation in image quality caused by the characteristic variation.

Further, in the display device 1, all of the drive transistors DRTr inthe display section 10 are provided to allow the channels CH to extendin the same direction as one another. This makes it possible to suppressthe characteristic variation (variation in characteristics such as thethreshold voltage Vth and the mobility μ) of the drive transistor DRTr.It is accordingly possible to reduce the risk of degradation in imagequality. The detail thereof is described below.

The characteristics variation of the drive transistor DRTr may belargely influenced by, for example, a step of forming the polysilicon203 in the process of forming the transistor. In this step, first, anamorphous silicon layer may be formed on the insulating layer 202 (FIG.3). Then, annealing treatment may be performed on the amorphous siliconlayer by an excimer laser anneal (ELA) apparatus to form the polysilicon203. Then, ions may be implanted into the channels CH of the polysilicon203 and lightly doped drain (LDD) in the vicinity of the channels CH byan ion implantation apparatus. Further, ions may be implanted into thevicinity of the contact 205 in the polysilicon 203 by an ion dopingapparatus. At this occasion, the treatment by the ELA apparatus mayinfluence the characteristic variation of the drive transistor DRTr.

FIG. 8 schematically illustrates the treatment by the ELA apparatus.FIG. 8 illustrates a case where a plurality of display sections 10 areformed on a large glass substrate 99. As illustrated in FIG. 8, the ELAapparatus may perform annealing treatment on the entire surface of theglass substrate 99 by scanning the glass substrate 99 in a scanningdirection D1 while turning on or off a strip-shaped laser beam (beamLB1) at, for example, about several hundred Hz. More specifically, inthe scanning, the ELA apparatus may shift a position of a shot of thestrip-shaped beam LB1 to allow the strip-shaped beam LB1 in a certainshot to be partially overlapped with the strip-shaped beam LB1 inprevious shot. At this time, the energy E of the laser beam may bevaried for each shot, which may cause mutual difference betweenuniformity of the energy E in the same direction as the scanningdirection D1 and uniformity of the energy E in the directionintersecting the scanning direction D1. As a result, there is risk thatcharacteristics of the drive transistor in which the channels CH extendin the same direction as the scanning direction D1 is different from thecharacteristics of the drive transistor in which the channels CH extendin the direction intersecting the scanning direction D1.

FIGS. 9A and 9B each illustrate relationship between arrangement of thedrive transistors DRTr in the respective sub-pixels 11 and the scanningdirection D1. In the configuration of FIG. 9A, the channels CH of thedrive transistors DRTr may be so provided as to extend in the directionorthogonal to the scanning direction D1. In the configuration of FIG.9B, the channels CH of the drive transistors DRTr may be so provided asto extend in the same direction as the scanning direction D1. In thisway, in the display section 10, all of the drive transistors DRTr in thedisplay section 10 may be provided to allow the channels CH to extend inthe same direction. In other words, drive transistors DRTr different inthe extending direction of the channel CH do not coexist in the displaysection 10. This makes it possible to suppress, in the display device 1,characteristics variation between the drive transistors DRTr and toreduce the risk of degradation in image quality due to thecharacteristics variation of the drive transistor DRTr.

As illustrated in FIGS. 9A and 9B, in this example, the channels CH ofthe drive transistors DRTr extend in the direction orthogonal to thescanning direction D1 (FIG. 9A) or in the same direction as the scanningdirection D1; however, the direction is not limited thereto.Alternatively, the channels CH of the drive transistors DRTr may beoriented to any other direction. The direction of the channels CH may bedetermined in consideration of, for example, image quality.

Further, in the display device 1, the polysilicon 203 of the drivetransistor DRTr is folded in the region where the gate 201 is notprovided, which makes it possible to suppress characteristic variationof the drive transistor DRTr and to reduce the risk of degradation inimage quality. More specifically, in manufacturing process, in additionto the channels CH, the folded portion W1 (FIG. 7) may be also subjectedto annealing treatment by the ELA apparatus. Accordingly, thepolysilicon 203 of the drive transistor DRTr may include both a portionextending in the direction intersecting the scanning direction D1 and aportion extending in the same direction as the scanning direction D1.The folded portion W1, however, may be low in resistance due to ionimplantation and may not function as the channel CH. Therefore, thefolded portion W1 less influences the characteristics of the drivetransistor DRTr. As a result, in the display device 1, it is possible tosuppress the characteristic variation of the drive transistor DRTrcaused by the folded portion W1, and to reduce the risk of degradationin image quality caused by the characteristic variation of the drivetransistor DRTr.

Effects

As described above, in the present embodiment, the plurality of channelsare coupled in series to configure the drive transistor, which makes itpossible to effectively utilize limited space to achieve the drivetransistor with long channel length. This allows for reduction of riskof degradation in image quality.

Also, in the above-described embodiment, the polysilicon of the drivetransistor is folded in the region where the gate is not provided, whichmakes it possible to suppress characteristic variation of the drivetransistor. This allows for reduction of risk of degradation in imagequality.

Further, in the above-described embodiment, all of the drive transistorsin the display section are provided to allow the channels thereof toextend in the same direction, which makes it possible to suppresscharacteristic variation of the drive transistor. This allows forreduction of risk of degradation in image quality.

Modification 1-1

In the above-described embodiment, three channels CH are coupled inseries; however the number of channels is not limited thereto.Alternatively, two or four or more channels CH may be coupled in series.FIG. 10 illustrates an example of a case where two channels CH arecoupled in series to each other. Also in this case, effects similar tothose in the above-described embodiment are obtainable.

Modification 1-2

In the above-described embodiment, as illustrated in FIG. 9, thechannels CH of the drive transistor DRTr extend in a longitudinaldirection of FIG. 9; however, the direction is not limited thereto. Forexample, as illustrated in FIG. 11, the channels CH of the drivetransistor DRTr may extend in a horizontal direction of the figure.

Modification 1-3

In the above-described embodiment, the plurality of channels CH coupledin series are juxtaposed in the same layer to configure the drivetransistor DRTr; however, the configuration is not limited thereto.Alternatively, the plurality of channels CH may be provided in thelamination direction to configure the drive transistor DRTr. The presentmodification is described in detail below by taking some specificexamples.

FIG. 12A illustrates a schematic sectional structure of a drivetransistor DRTrA according to the present modification. The drivetransistor DRTrA may include gates 301 and 305 and polysilicons 303 and307. The gate 301 may be selectively formed on the transparent substrate200. The insulating layer 302 may be provided on the transparentsubstrate 200 and the gate 301, and the polysilicon 303 may beselectively formed on the insulating layer 302. The insulating layer 304may be provided on the insulating layer 202 and the polysilicon 303, andthe gate 305 may be selectively formed on the insulating layer 304. Theinsulating layer 306 may be provided on the insulating layer 304 and thegate 305, and the polysilicon 307 may be provided on the insulatinglayer 306. The insulating layer 308 may be provided on the insulatinglayer 306 and the polysilicon 307. Further, in FIG. 12A, contacts 309and 312 may be so provided respectively at a left end and a right end ofthe polysilicon 303 as to penetrate the insulating layers 304, 306, and308. Likewise, contacts 310 and 311 may be so provided respectively at aleft end and a right end of the polysilicon 307 as to penetrate theinsulating layer 308. Further, the contact 309 and the contact 310 maybe coupled to each other on the insulating layer 308. The contact 311may be, for example, a drain terminal of the drive transistor DRTrA, andthe contact 312 may be, for example, a source terminal of the drivetransistor DRTrA. Although not illustrated, the gates 301 and 305 may becoupled to each other and coupled to a gate terminal.

Thus, the gate 301, the insulating layer 302, and the polysilicon 303may configure a transistor of a bottom-gate structure. Likewise, thegate 305, the insulating layer 306, and the polysilicon 307 mayconfigure a transistor of a bottom-gate structure. In the drivetransistor DRTrA, the two channels CH coupled in series to each othermay be provided in the lamination direction in this way.

Further, in FIG. 12A, for example, the thickness of the insulating layer302 may be different between in the region where the gate 301 isprovided and in the region where the gate 302 is not provided; however,the thickness is not limited thereto. For example, similarly to FIG. 3,the thickness of the insulating layer 302 may be substantially uniform.

FIG. 12B illustrates a schematic sectional structure of a drivetransistor DRTrB according to the present modification. The drivetransistor DRTrB may include gates 321 and 327 and polysilicons 323 and325. The gate 321 may be selectively formed on the transparent substrate200. The insulating layer 322 may be provided on the transparentsubstrate 200 and the gate 321, and the polysilicon 323 may beselectively formed on the insulating layer 322. The insulating layer 324may be provided on the insulating layer 222 and the polysilicon 323, andthe polysilicon 325 may be selectively formed on the insulating layer324. The insulating layer 326 may be provided on the insulating layer324 and the polysilicon 325, and the gate 327 may be provided on theinsulating layer 326. The insulating layer 328 may be provided on theinsulating layer 326 and the gate 327. Further, in FIG. 12B, contacts329 and 332 may be so provided respectively at a left end and a rightend of the polysilicon 323 as to penetrate the insulating layers 324,326, and 328. Likewise, contacts 330 and 331 may be so providedrespectively at a left end and a right end of the polysilicon 325 as topenetrate the insulating layers 326 and 328. Further, the contact 329and the contact 330 may be coupled to each other on the insulating layer328. The contact 331 may be, for example, a drain terminal of the drivetransistor DRTrB, and the contact 332 may be, for example, a sourceterminal of the drive transistor DRTrB. Although not illustrated, thegates 321 and 327 may be coupled to each other and coupled to a gateterminal.

Thus, the gate 321, the insulating layer 322, and the polysilicon 323may configure a transistor of a bottom-gate structure, and the gate 327,the insulating layer 326, and the polysilicon 325 may configure atransistor of a top-gate structure. In the drive transistor DRTrB, twochannels CH coupled in series to each other may be provided in thelamination direction in this way.

In the drive transistor DRTrB, the gate 321, the polysilicon 323, thepolysilicon 325, and the gate 327 are provided in this order, whichmakes it possible to achieve simple operation. Specifically, in thedrive transistor DRTrA according to the above-described modification,since the gate 301, the polysilicon 303, the gate 305, and thepolysilicon 307 are provided in this order, the voltage of the gate 305may control generation of an inversion layer of the polysilicon 303 inaddition to generation of an inversion layer of the polysilicon 307. Inthis case, operation of the drive transistor DRTrA may becomecomplicated. In contrast, in the drive transistor DRTrB, since the gates321 and 327 are provided outside the polysilicons 323 and 325,respectively, the voltage of the gate 321 controls generation of aninversion layer in the polysilicon 323 and the voltage of the gate 327controls generation of an inversion layer in the polysilicon 325, whichmakes it possible to achieve simple operation.

FIG. 12C illustrates a schematic sectional structure of a drivetransistor DRTrC according to the present modification. The drivetransistor DRTrC may include a gate 344 and polysilicons 342 and 346.The insulating layer 341 may be provided on the transparent substrate200, and the polysilicon 342 may be selectively formed on the insulatinglayer 341. The insulating layer 343 may be provided on the insulatinglayer 341 and the polysilicon 342, and the gate 344 may be selectivelyformed on the insulating layer 343. The insulating layer 345 may beprovided on the insulating layer 243 and the gate 344, and thepolysilicon 346 may be selectively formed on the insulating layer 345.The insulating layer 347 may be provided on the insulating layer 345 andthe polysilicon 346. Further, in FIG. 12C, contacts 349 and 352 may beso provided respectively at a left end and a right end of thepolysilicon 342 as to penetrate the insulating layers 343, 345, and 347.Likewise, contacts 350 and 351 may be so provided respectively at a leftend and a right end of the polysilicon 346 as to penetrate theinsulating layer 347. Further, the contact 349 and the contact 350 maybe coupled to each other on the insulating layer 347. The contact 351may be, for example, a drain terminal of the drive transistor DRTrC, andthe contact 352 may be, for example, a source terminal of the drivetransistor DRTrC. Although not illustrated, the gate 344 may be coupledto a gate terminal.

Thus, the gate 344, the insulating layer 343, and the polysilicon 342may configure a transistor of a top-gate structure, and the gate 344,the insulating layer 345, and the polysilicon 346 may configure atransistor of a bottom-gate structure. At this time, the voltage of thegate 344 may control generation of inversion layers in the respectivetwo polysilicons 342 and 346. In the drive transistor DRTrC, the twochannels CH coupled in series to each other may be provided in thelamination direction in this way.

In the drive transistor DRTrC, the polysilicon 342, the gate 344, andthe polysilicon 346 may be provided in this order, and the generation ofthe inversion layers in the respective two polysilicons 342 and 346 maybe controlled with use of the voltage of the gate 344. In other words,two gates are provided in each of the drive transistors DRTrA and DRTrBaccording to the foregoing modifications, whereas only one gate isprovided in the drive transistor DRTrC according to the presentmodification. As a result, unlike the drive transistors DRTrA and DRTrBaccording to the foregoing modifications, a single step of forming thegate is necessary in manufacturing the drive transistor DRTrC, whichmakes it possible to simplify the manufacturing process.

Modification 1-4

In the above-described embodiment, as illustrated in FIG. 6, fourcircuit regions 15R, 15G, 15B, and 15W are arranged in two rows and twocolumns as with the four anodes 212R, 212G, 212B, and 212W; however, thelayout is not limited thereto. Alternatively, for example, asillustrated in FIGS. 13 and 14, the four anodes 212R, 212G, 212B, and212W may be arranged in two rows and two columns and four circuitregions 16R, 16G, 16B, and 16W may be arranged along a single direction.In this example, the circuit regions 16R, 16G, 16B, and 16W may beregions long in the longitudinal direction, and may be disposed side byside in this order in the lateral direction. In each of the circuitregions 16R, 16G, 16B, and 16W, the write transistor WSTr, the drivetransistor DRTr, and the capacitor Cs may be arranged in the samelayout. More specifically, in this example, the layout in the circuitregions 16R and 16B may be obtained by rotating the layout of thecircuit regions 16G and 16W by 180 degrees. The anodes 212R, 212G, 212B,and 212W may be respectively coupled to sources of the drive transistorsDRTr provided in the circuit regions 16R, 16G, 16B, and 16W through thecontact 205.

As illustrated in FIG. 14, in this example, the polysilicon 203 of thedrive transistor DRTr may be so provided as to extend in thelongitudinal direction without being folded. In other words, in thisexample, the circuit regions 16R, 16G, 16B, and 16W are each made longin the longitudinal direction, which makes it possible to provide thedrive transistor DRTr with long channel length L without folding thepolysilicon 203.

Modification 1-5

In the above-described embodiment, the four sub-pixels 11R, 11G, 11B,and 11W are arranged in two rows and two columns; however, the layout isnot limited thereto. Alternatively, for example, as illustrated in FIG.15, the four sub-pixels 11R, 11G, 11B, and 11W may be arranged in asingle direction. In this example, the sub-pixels 11R, 11G, 11B, and 11Wmay be made long in the longitudinal direction, and may be juxtaposed inthis order in the lateral direction. In this case, the circuit regionsmay be arranged in two rows and two columns as illustrated in FIG. 9, ormay be arranged in a single direction as illustrated in FIG. 14.

Modification 1-6

In the above-described embodiment, the pixel Pix is configured of foursub-pixels 11R, 11G, 11B, and 11B of red (R), green (G), blue (B), andwhite (W); however, the configuration is not limited thereto.Alternatively, as illustrated in FIGS. 16A and 16B, the pixel Pix may beconfigured of three sub-pixels 11R, 11G, and 11B of red (R), green (G),and blue (B). Moreover, the configuration of the light emitting layer230 is not limited thereto, and alternatively, for example, as with alight emitting layer 240 illustrated in FIGS. 17A and 17B, a red lightemitting layer, a green light emitting layer, and a blue light emittinglayer may be provided in regions respectively corresponding to the colorfilters 218 of red (R), green (G), and blue (B).

Modification 1-7

In the above-described embodiment, the light emitting layer 230 emittingwhite (W) light is provided; however, the configuration is not limitedthereto. Alternatively, for example, as illustrated in FIGS. 18A to 18D,a light emitting layer 250 that includes a yellow light emitting layeremitting yellow (Y) light and a blue light emitting layer emitting blue(B) light may be provided. The present modification is described indetail below.

FIGS. 18A to 18D each schematically illustrate an example in which thepixel Pix is configured using four sub-pixels 11R, 11G, 11B, and 11Y ofred (R), green (G), blue (B), and yellow (Y). FIG. 18A illustrates anexample in which the four sub-pixels 11R, 11G, 11B, and 11Y are arrangedin two rows and two columns. FIG. 18B illustrates an example in whichthe four sub-pixels 11R, 11G, 11B, and 11Y are arranged in a singledirection. FIG. 18C illustrates an example in which the sub-pixels 11R,11Y, and 11G are arranged in the lateral direction and the sub-pixel 11Bis so provided as to be adjacent to all of the sub-pixels 11R, 11Y, and11G in the longitudinal direction. FIG. 18D illustrates a sectionalstructure of the pixel Pix in any of the cases of FIGS. 18A to 18C. Inthis case, as illustrated in FIGS. 18A to 18D, the yellow light emittinglayer emitting yellow (Y) light may be provided in a regioncorresponding to the color filters 218 of red (R), green (G), and yellow(Y), and the blue light emitting layer emitting blue (B) light may beprovided in a region corresponding to the blue (B) color filter 218,which makes it possible to configure the light emitting layer 250. As aresult, in the sub-pixel 11R, yellow (Y) light may be passed through thered (R) color filter 218, which may result in emission of red (R) light.In the sub-pixel 11G, yellow (Y) light may be passed through the green(G) color filter 218, which may result in emission of green (G) light.In the sub-pixel 11Y, yellow (Y) light may be passed through the yellow(Y) color filter 218, which may result in emission of yellow (Y) light.In the sub-pixel 11B, blue (B) light may be passed through the blue (B)color filter 218, which may result in emission of blue (B) light.Moreover, color filters 218 of yellow (Y) and blue (B) may be omitted.

FIGS. 19A to 19C each schematically illustrate an example in which thepixel Pix is configured using three sub-pixels 11R, 11G, and 11B of red(R), green (G), and blue (B). FIG. 19A illustrates an example in whichthe sub-pixels 11R, 11G, and 11B are arranged in the lateral direction.FIG. 19B illustrates an example in which the sub-pixels 11R and 11G arearranged in the lateral direction and the sub-pixel 11B is so providedas to be adjacent to both the sub-pixels 11R and 11G in the longitudinaldirection. FIG. 19C illustrates a sectional structure of the pixel Pixin any of the cases of FIGS. 19A and 19B. In this case, as illustratedin FIGS. 19A to 19C, the yellow light emitting layer emitting yellow (Y)light may be provided in the region corresponding to the color filters218 of red (R) and green (G), and the blue light emitting layer emittingblue (B) light may be provided in the region corresponding to the blue(B) color filter 218, which makes it possible to configure the lightemitting layer 250. As a result, in the sub-pixel 11R, the yellow (Y)light may be passed through the red (R) color filter 218, which mayresult in emission of red (R) light. In the sub-pixel 11G, the yellow(Y) light may be passed through the green (G) color filter 218, whichmay result in emission of green (G) light. In the sub-pixel 11B, theblue (B) light may be passed through the blue (B) color filter 218,which may result in emission of blue (B) light. Moreover, the blue (B)color filter 218 may be omitted.

Modification 1-8

The layout of the plurality of channels CH of the drive transistor DRTris not limited to the layout illustrated in FIG. 6. Alternatively, forexample, as illustrated in FIG. 20A, two channels CH may extend indirections different from each other. In this example, the polysilicon203 may be bent by 90 degrees between the two channels CH to allow thetwo channels CH to extend in different directions. Also, for example, asillustrated in FIG. 20B, the polysilicon 203 may be bent right by 90degrees after being bent left by 90 degrees between the two channels CH.Even in such a case, it is possible to effectively utilize limited spaceto achieve the drive transistor DRTr with long channel length L. Thisallows for reduction of risk of degradation in image quality.

2. Second Embodiment

Next, a display device 2 according to a second embodiment is described.In the present embodiment, the gate insulating film of the drivetransistor may have a thickness larger than that of the gate insulatingfilm of the write transistor. Other configurations may be similar tothose in the above-described first embodiment (FIG. 1 and otherfigures). Moreover, like components as those of the display device 1according to the first embodiment are denoted by like numerals, and thedescription thereof is appropriately omitted.

As illustrated in FIG. 1, the display device 2 may include a displaysection 50. The display section 50 may include the plurality of pixelsPix arranged in a matrix, and the pixels Pix each may include foursub-pixels 11 (11R, 11G, 11B, and 11W), as with the display section 10according to the first embodiment. Each of the sub-pixels 11 may includea drive transistor DRTr2 and a write transistor WSTr2. The drivetransistor DRTr2 and the write transistor WSTr2 each may be a transistorhaving a top-gate structure. The gate insulating film of the drivetransistor DRTr2 may have a thickness larger than that of the gateinsulating film of the write transistor WSTr2.

FIG. 21 illustrates schematic sectional structures of the drivetransistor DRTr2 and the write transistor WSTr2.

The drive transistor DRTr2 may include a polysilicon 401, insulatinglayers 402 and 403, and a gate 404. In the drive transistor DRTr2, thepolysilicon 401 may be selectively formed on the transparent substrate200. The insulating layers 402 and 403 may be provided in this order onthe transparent substrate 200 and the polysilicon 401, and the gate 404may be selectively formed on the insulating layer 403. A dielectricconstant of the insulating layer 403 may be desirably lower than adielectric constant of the insulating layer 402. The gate insulatingfilm of the drive transistor DRTr2 may be configured of two insulatinglayers 402 and 403 in this way.

The write transistor WSTr2 may include a polysilicon 401, an insulatinglayer 402, and a gate 404. In the write transistor WSTr2, thepolysilicon 401 may be selectively formed on the transparent substrate200. The insulating layer 402 may be provided on the transparentsubstrate 200 and the polysilicon 401, and the gate 404 may beselectively formed on the insulating layer 402. The gate insulating filmof the write transistor WSTr2 may be configured of one insulating layer402 in this way.

Moreover, in this example, the insulating layer 402 is configured of asingle layer; however, the configuration is not limited thereto.Alternatively, the insulating layer 402 may be configured of a pluralityof layers. Specifically, for example, the insulating layer 402 may beconfigured using an upper layer formed of silicon nitride (SiNx) and alower layer formed of silicon oxide (SiO2). Likewise, the insulatinglayer 403 is configured of a single layer; however, the configuration isnot limited thereto. Alternatively, the insulating layer 403 may beconfigured of a plurality of layers.

FIG. 22 illustrates an example of steps of manufacturing the drivetransistor DRTr2 and the write transistor WSTr2. First, in the drivetransistor DRTr2 and the write transistor WSTr2, the polysilicon 401 andthe insulating layers 402 and 403 may be formed in this order ((A) ofFIG. 22). Then, in the write transistor WSTr2, the insulating layer 403may be removed by etching ((B) of FIG. 22). Next, in the drivetransistor DRTr2 and the write transistor WSTr2, the gate 404 and theinsulating layer 405 may be formed ((C) of FIG. 22). Thereafter, thecontact 205 may be formed to complete the drive transistor DRTr2 and thewrite transistor WSTr2 as illustrated in FIG. 21.

As described above, in the display device 2, the gate insulating film ofthe drive transistor DRTr2 is formed to have a thickness larger thanthat of the gate insulating film of the write transistor WSTr2, whichmakes it possible to reduce the gate insulating film capacity Cox of thedrive transistor DRTr2. This allows for reduction of risk of degradationin image quality. In other words, in the display device 2, it ispossible to reduce the gate insulating film capacity Cox of the drivetransistor DRTr. This makes it possible to lower sensitivity of thegate-source voltage Vgs with respect to the drain current Ids, asrepresented by the expression (1). Therefore, even if the pixel voltageVsig is varied for each data line DTL, it is possible to reduce the riskthat a stripe extending in the column direction of the sub-pixels 11occurs, for example, in the display image. This allows for reduction ofrisk of degradation in image quality.

Further, in the display device 2, the insulating layers 402 and 403 areprovided in the drive transistor DRTr2 and the write transistor WSTr2,and the insulating layer 403 is then removed from the write transistorWSTr2 by etching. At this occasion, the insulating layer 402 remains inthe write transistor WSTr2, which makes it possible to reduce the riskof contamination of the polysilicon 401 of the write transistor WSTr2.Also, the gate 404 is formed in each of the drive transistor DRTr2 andthe write transistor WSTr2 after the insulating layer 403 is removedfrom the write transistor WSTr2, which makes it possible to form thegate 404 of each of the drive transistor DRTr2 and the write transistorWSTr2 at a time. Thus, a single step of forming the gate is necessary,which makes it possible to simplify the manufacturing process.

As described above, in the present embodiment, the gate insulating filmof the drive transistor is formed to have a thickness larger than thatof the gate insulating film of the write transistor, which makes itpossible to reduce the gate insulating film capacity of the drivetransistor. This allows for reduction of risk of degradation in imagequality.

Further, in the present embodiment, the insulating layers 402 and 403are formed in each of the drive transistor and the write transistor, andthe insulating layer 403 is then removed from the write transistor toallow the gate to be formed in each of the drive transistor and thewrite transistor. This allows for reduction of risk of contamination ofthe polysilicon. In addition, a single step of forming the gate isnecessary, which makes it possible to simplify the manufacturingprocess.

Modification 2-1

In the above-described embodiment, in the write transistor WSTr2, theinsulating layer 403 is removed by etching to form the gate insulatingfilm of the drive transistor WSTr2 to have a thickness larger than thatof the gate insulating film of the write transistor WSTr2; however, theconfiguration is not limited thereto. The present modification isdescribed below by taking some examples.

FIG. 23 illustrates schematic sectional structures of a drive transistorDRTr2A and a write transistor WSTr2A according to the presentmodification. The drive transistor DRTr2A may include insulating layers412 and 413. In the drive transistor DRTr2A, the insulating layers 412and 413 may be provided in this order on the transparent substrate 200and the polysilicon 401, and the gate 404 may be selectively formed onthe insulating layer 413. A dielectric constant of the insulating layer412 may be desirably lower than that of the insulating layer 413. Thegate insulating film of the drive transistor DRTr2A may be configured ofthe two insulating layers 412 and 413 in this way. The write transistorWSTr2A may include the insulating layer 413. In the write transistorWSTr2A, the insulating layer 413 may be provided on the transparentsubstrate 200 and the polysilicon 401, and the gate 404 may beselectively formed on the insulating layer 413. The gate insulating filmof the write transistor WSTr2A may be configured of one insulating layer413 in this way.

FIG. 24 illustrates an example of steps of manufacturing the drivetransistor DRTr2A and the write transistor WSTr2A. First, in each of thedrive transistor DRTr2A and the write transistor WSTr2A, the polysilicon401 and the insulating layer 412 may be formed in this order ((A) ofFIG. 24). Then, the insulating layer 412 may be all removed from thewrite transistor WSTr2A by etching ((B) of FIG. 24). Subsequently, ineach of the drive transistor DRTr2A and the write transistor WSTr2A, theinsulating layer 413 may be formed ((C) of FIG. 24), and the gate 404and the insulating layer 405 may be then formed ((D) of FIG. 24).

Also in this case, it is possible to reduce the gate insulating filmcapacity Cox of the drive transistor DRTr2A, which makes it possible toreduce the risk of degradation in image quality.

In the steps of manufacturing the drive transistor DRTr2A and the writetransistor WSTr2A, as illustrated in FIG. 24, the polysilicon 401 andthe insulating layer 412 are formed, and then the insulating layer 412is all removed from the write transistor WSTr2A by etching. However, thestep is not limited thereto, and alternatively, for example, as with adrive transistor DRTr2B and a write transistor WSTr2B illustrated inFIGS. 25 and 26, the polysilicon 401 and the insulating layer 412 may beformed in the drive transistor DRTr2B and the write transistor WSTr2B,and a portion of the insulating layer 412 may be then removed from thewrite transistor WSTr2B by etching to allow a thin insulating layer 412Ato be left. In this example, as illustrated in FIG. 25, the writetransistor WSTr2B may include the insulating layers 412A and 413. Theinsulating layer 412A may be formed at the same time as the insulatinglayer 412 in the drive transistor DRTr2B. As described above, the gateinsulating film of the write transistor WSTr2B may be configured of twoinsulating layers 412A and 413. A portion of the insulating layer 412(the insulating layer 412A) is left in such a way, which makes itpossible to reduce the risk of contamination of the polysilicon 401 ascompared with a case where the insulating layer 412 is all removed.

FIG. 27 illustrates a schematic sectional structure of a drivetransistor DRTr2C and a write transistor WSTr2C according to the presentmodification. The drive transistor DRTr2C may include insulating layers432 and 434 and a gate 435. In the drive transistor DRTr2C, theinsulating layers 432 and 434 may be provided in this order on thetransparent substrate 200 and the polysilicon 401, and the gate 435 maybe selectively formed on the insulating layer 434. A dielectric constantof the insulating layer 434 may be desirably lower than that of theinsulating layer 432. The gate insulating film of the drive transistorDRTr2C may be configured of the two insulating layers 432 and 434 inthis way. The write transistor WSTr2C may include the insulating layer432 and a gate 433. In the write transistor WSTr2C, the insulating layer432 may be provided on the transparent substrate 200 and the polysilicon401, and the gate 433 may be selectively formed on the insulating layer432. The gate insulating film of the write transistor WSTr2C may beconfigured of one insulating layer 432 in this way.

FIG. 28 illustrates an example of steps of manufacturing the drivetransistor DRTr2C and the write transistor WSTr2C. First, in each of thedrive transistor DRTr2C and the write transistor WSTr2C, the polysilicon401 and the insulating layer 432 may be formed in this order ((A) ofFIG. 28). Then, the gate 433 may be formed in the write transistorWSTr2C, and the insulating layer 434 may be then formed in each of thedrive transistor DRTr2C and the write transistor WSTr2C ((B) of FIG.28). Subsequently, the gate 435 may be formed in the drive transistorDRTr2C, and the insulating layer 405 may be then formed in each of thedrive transistor DRTr2C and the write transistor WSTr2C ((C) of FIG.28).

Also in this case, it is possible to reduce the gate insulating filmcapacity Cox of the drive transistor DRTr2C, which makes it possible toreduce the risk of degradation in image quality.

Modification 2-2

The drive transistor DRTr2 and the write transistor WSTr2 each having atop-gate structure are used in the above-described embodiment; however,the structure of the transistor is not limited thereto. Alternatively,for example, the drive transistor DRTr2 and the write transistor WSTr2each having a bottom-gate structure may be used.

Other Modifications

Any of the modifications according to the first embodiment describedabove may apply to the display device 2 according to the above-describedembodiment.

3. Third Embodiment

Next, a display device 3 according to a third embodiment is described.In the present embodiment, grains (crystal grains) in the polysilicon ofthe drive transistor may be made smaller in size than grains of theother transistors. Other configurations may be similar to those in theabove-described first embodiment (FIG. 1 and other figures). Moreover,like components as those of the display device 1 according to the firstembodiment are denoted by like numerals, and the description thereof isappropriately omitted.

As illustrated in FIG. 1, the display device 3 may include a displaysection 60. The display section 60 may include the plurality of pixelsPix arranged in a matrix, and each of the pixels Pix may include thefour sub-pixels 11 (11R, 11G, 11B, and 11W), as with the display section10 according to the first embodiment. Each of the sub-pixels 11 mayinclude a drive transistor DRTr3 and a write transistor WSTr3. In thisexample, grains G (crystal grains) of the polysilicon 203 in the drivetransistor DRTr3 may be made smaller in size than grains G of thepolysilicon 203 in the write transistor WSTr3.

FIG. 29 illustrates an example of the grains (crystal grains) of thepolysilicon 203. In this example, the grains G having random shapes maybe disposed at random in the polysilicon 203. Moreover, the grain G isnot limited thereto, and alternatively, grains with similar shapes toone another may be orderly arranged. In the step of manufacturing thedrive transistor DRTr3 and the write transistor WSTr3, the amorphoussilicon layer may be formed on the insulating layer 202 (FIG. 3), andthe annealing treatment may be performed on the amorphous silicon layerby the ELA apparatus to allow the grains G to grow, which results information of the polysilicon 203, as with the display device 1 accordingto the above-described first embodiment. At this time, a laser beam maybe applied to the drive transistor DRTr3 and the write transistor WSTr3under different application conditions from each other. Specifically,for example, a laser beam with low energy may be applied to the drivetransistor DRTr3, whereas a laser beam with high energy may be appliedto the write transistor WSTr3. Moreover, application is not limitedthereto, and alternatively, for example, a laser beam with fixed energymay be applied to the drive transistor DRTr3 and the write transistorWSTr3 while the number of times of application to the drive transistorDRTr3 may be decreased to shorten the total application time and thenumber of times of application to the write transistor WSTr3 may beincreased to prolong the total application time. This makes it possibleto make the grains G of the drive transistor DRTr3 smaller in size thanthe grains G of the write transistor WSTr3.

As described above, in the display device 3, the grains G of the drivetransistor DRTr3 are thus made smaller in size than the grains G of thewrite transistor WSTr3, which makes it possible to reduce the risk ofdegradation in image quality. Specifically, when the grains G are madesmaller in size, it is possible to decrease the mobility μ of carrier(for example, electron) in the polysilicon 203. In other words, thecarrier is able to move fast in each grain G, but the moving speed isdecreased at border between the grains G. Accordingly, as the grains Gare made smaller, the number of borders between grains G to be crossedby the carrier is increased, and the mobility μ is thus decreased.Therefore, in the display device 3, the mobility μ of the drivetransistor DRTr3 is decreased, which makes it possible to lowersensitivity of the gate-source voltage Vgs with respect to the draincurrent Ids as represented by the expression (1). This allows forreduction in the possibility that a stripe extending in the columndirection of the sub-pixel 11 occurs in the display image even if thepixel voltage Vsig is varied for each data line DTL, which makes itpossible to reduce the risk of degradation in image quality.

Further, as mentioned above, the grains G of the polysilicon 203 in thedrive transistor DRTr3 are made smaller in size than the grains G of thepolysilicon 203 in the write transistor WSTr3, which makes it possibleto suppress variation in mobility μ. In other words, the mobility μ mayvary depending on the number of borders between the grains G to becrossed by the carrier. Therefore, as the grains G are made smaller insize, the number of borders between the grains G to be crossed by thecarrier is increased to reduce variation in the number of borders, whichmakes it possible to suppress the variation in mobility μ. As a result,it is possible to suppress degradation in image quality caused byvariation in mobility μ of the drive transistor DRTr3.

FIG. 30 illustrates an implementation example of the display device 3.In this example, peripheral circuits 71 to 74 may be disposed on leftside, upper side, right side, and lower side of the display section 60,respectively. The peripheral circuit 71 may be, for example, the scanline drive section 23, the peripheral circuit 73 may be, for example,the power line drive section 26, and the peripheral circuit 74 may be,for example, the data line drive section 27. As mentioned above, in thedisplay section 60, the grains G of the drive transistor DRTr3 may bemade smaller in size than those of the write transistor WSTr3. In theperipheral circuits 71 to 74, for example, the grains G of thetransistors used in the respective circuits may be equivalent in size tothe grains G of the write transistor WSTr3 in the display section 60.This makes it possible to make the mobility μ of the drive transistorDRTr3 of the display section 60 smaller than the mobility μ of thetransistors other than the drive transistor DRTr3. Thus, in the displaydevice 3, the mobility μ of only the drive transistor DRTr3 is madesmall while the mobility μ of the transistors other than the drivetransistor DRTr3 is maintained to a large value, which makes it possibleto suppress degradation in image quality while suppressing possibilityof influence to the operation of the transistors other than the drivetransistor DRTr3.

As described above, in the present embodiment, the grains of the drivetransistor are made smaller in size than the grains of the writetransistor, which makes it possible to decrease the mobility of thedrive transistor. This allows for reduction of risk of degradation inimage quality.

Modification 3-1

In the above-described embodiment, the mobility μ of the drivetransistor DRTr3 of the display section 60 is decreased, and themobility μ of the write transistor WSTr3 of the display section 60 andthe mobility μ of the transistors in the respective peripheral circuits71 to 74 are increased; however, the mobility μ is not limited thereto.Alternatively, for example, the mobility μ of the drive transistor DRTr3and the write transistor WSTr3 of the display section 60 may bedecreased and the mobility μ of the transistors in the respectiveperipheral circuits 71 to 74 may be increased. Also, for example, themobility μ of the drive transistor DRTr3 and the write transistor WSTr3of the display section 60 and the mobility μ of the transistors in therespective peripheral circuits 71 and 73 may be decreased as well as themobility μ of the transistors in the respective peripheral circuits 72and 74 may be increased. Further, for example, the mobility μ of thedrive transistor DRTr3 and the write transistor WSTr3 of the displaysection 60 and the mobility μ of the transistors in the respectiveperipheral circuits 72 and 74 may be decreased as well as the mobility μof the transistors in the respective peripheral circuits 71 and 73 maybe increased.

Modification 3-2

In the above-described embodiment, a laser beam is applied to the drivetransistor DRTr3 and the write transistor WSTr3 under the differentapplication conditions from each other to make the grains G of thepolysilicon 203 in the drive transistor DRTr3 smaller than the grains Gof the polysilicon 203 in the write transistor WSTr3. However, theconfiguration is not limited thereto. The present modification isdescribed in detail below.

FIG. 31 illustrates schematic sectional structures of a drive transistorDRTr3A and a write transistor WSTr3A according to the presentmodification. FIG. 32 illustrates a configuration example of the drivetransistor DRTr3A. The drive transistor DRTr3A and the write transistorWSTr3A each may have a top-gate structure.

The drive transistor DRTr3A may include an electrically-conductive layer501, an insulating layer 502, a polysilicon 503, an insulating layer504, a gate 505, and an insulating layer 506. In the drive transistorDRTr3A, the electrically-conductive layer 501 may be selectively formedon the transparent substrate 200. The electrically-conductive layer 501may be formed of, for example, molybdenum (Mo). Further, the insulatinglayer 502 may be provided on the transparent substrate 200 and theelectrically-conductive layer 501. The polysilicon 503 may beselectively formed on the insulating layer 502, and the insulating layer504 may be provided on the insulating layer 502 and the polysilicon 503.Further, the gate 505 may be selectively formed on the insulating layer504, and the insulating layer 506 may be provided on the insulatinglayer 504 and the gate 505.

As described above, the electrically-conductive layer 501 may beprovided below the polysilicon 503 in the drive transistor DRTr3A. Inthis example, as illustrated in FIG. 32, the electrically-conductivelayer 501 may be provided in a region corresponding to a region wherethe gate 505 is provided. In other words, the electrically-conductivelayer 501 may be provided below the channel CH of the drive transistorDRTr3A. Moreover, the configuration is not limited thereto, andalternatively, for example, the electrically-conductive layer 501 may beprovided below at least a portion of the channel CH.

The write transistor WSTr3A may include the insulating layer 502, thepolysilicon 503, the insulating layer 504, the gate 505, and theinsulating layer 506. In other words, unlike the drive transistorDRTr3A, the write transistor WSTr3A may not include theelectrically-conductive layer 501.

In the step of manufacturing the drive transistor DRTr3A and the writetransistor WSTr3A, for example, as with the display device 1 accordingto the first embodiment, an amorphous silicon layer may be formed on theinsulating layer 502, and annealing treatment may be performed on theamorphous silicon layer by the ELA apparatus to allow the grains G togrow, which results in formation of the polysilicon 503. At this time, alaser beam may be applied to the drive transistor DRTr3A and the writetransistor WSTr3A under the same application condition. Then, in thedrive transistor DRTr3A, heat generated in the amorphous silicon layer(the polysilicon 503) may be transferred to the electrically-conductivelayer 501 through the insulating layer 502 and dissipated. Accordingly,in the drive transistor DRTr3A, the amorphous silicon layer may beeasily heated and cooled as compared with the amorphous silicon layer ofthe write transistor WSTr not including the electrically-conductivelayer 501. In other words, temperature of the amorphous silicon layer ofthe drive transistor DRTr3A at the time when being irradiated with thelaser beam may become lower than temperature of the amorphous siliconlayer of the write transistor WSTr at the time when being irradiatedwith the laser beam under the same application condition. This makes itpossible to make the grains G of the drive transistor DRTr3A smaller insize than the grains G of the write transistor WSTr3A.

As described above, in the present modification, theelectrically-conductive layer 501 is provided below the polysilicon 503in the drive transistor DRTr3A, which makes it possible to dissipateheat in the drive transistor DRTr3A as compared with the writetransistor WSTr3A. This makes it possible to employ the same applicationcondition at the time when the laser beam is applied to the drivetransistor DRTr3A and at the time when the laser beam is applied to thewrite transistor WSTr3A, which makes it possible to simplify themanufacturing process.

The electrically-conductive layer 501 of each of the sub-pixels 11 maybe desirably electrically coupled to the electrically-conductive layer501 of the other sub-pixel 11. This makes it easier to dissipate heatwhen the laser beam is applied in the manufacturing process. Moreover,the configuration is not limited thereto, and theelectrically-conductive layer 501 of each of the sub-pixels 11 may notbe coupled to the electrically-conductive layer 501 of the othersub-pixel 11.

Further, the electrically-conductive layer 501 may be desirably suppliedwith a predetermined direct-current voltage, for example. Specifically,for example, the electrically-conductive layer 501 may be grounded. Thisallows for further stabilization of the operation of each sub-pixel 11.Also, for example, a predetermined positive voltage or a predeterminednegative voltage may be applied. This allows for adjustment of thethreshold Vth of the drive transistor DRTr3A. Moreover, the voltage isnot limited thereto, and an alternate-current voltage may be applied tothe electrically-conductive layer 501 or the electrically-conductivelayer 501 may be electrically floated.

Also, in this example, as illustrated in FIG. 32, theelectrically-conductive layer 501 is provided in the region where thechannel CH of the drive transistor DRTr3A is provided; however, theconfiguration is not limited thereto. Alternatively, for example, aswith a drive transistor DRTr3B illustrated in FIG. 33, theelectrically-conductive layer 501 may be provided in a wider regionincluding the region where the folded portion W1 of the polysilicon 503is provided and the region where the contact 205 is provided.

Other Modifications

Any of the modifications according to the above-described first andsecond embodiments may be applied to the display device 3 according tothe above-described embodiment.

4. Application Examples

Next, application examples of the display device described in any of theembodiments and the modifications described above are described.

FIG. 34 illustrates an appearance of a television to which the displaydevice according to any of the embodiments and the modificationsdescribed above is applied. The television may include, for example, apicture display screen section 510 that includes a front panel 511 and afilter glass 512, and the picture display screen section 510 may beconfigured of the display device according to any of the embodiments andthe modifications described above.

The display device according to any of the embodiments and themodifications described above is applicable to electronic apparatuses invarious fields, for example, a digital camera, a notebook personalcomputer, a mobile terminal device such as a mobile phone, a portablegame machine, and a video camera. In other words, the display deviceaccording to any of the embodiments and the modifications describedabove is applicable to electronic apparatuses in various fields thatdisplay a picture.

Hereinabove, although the technology has been described with referenceto some embodiments, modifications, and application examples toelectronic apparatuses, the technology is not limited to the embodimentsand other examples, and various modifications may be made.

For example, in the above-described embodiments, the sub-pixel 11 isconfigured using the N-channel MOS drive transistor DRTr and theN-channel MOS write transistor WSTr; however, the transistor is notlimited thereto. Alternatively, for example, as illustrated in FIGS. 35and 36, a sub-pixel 12 may be configured using a P-channel MOS drivetransistor DRRrP and a P-channel MOS write transistor WSTrP. The writetransistor WSTrP may have a gate coupled to the scan line WSL, a sourcecoupled to the data lien DTL, and a drain coupled to a gate of the drivetransistor DRTrP and one end of the capacitor Cs. The drive transistorDRTrP may have the gate coupled to the drain of the write transistorWSTrP and the one end of the capacitor Cs, a drain coupled to the anodeof the light emitting element 30, and a source coupled to the other endof the capacitor Cs and the power line PL. As illustrated in FIG. 36,the drive section 20 may write the pixel voltage Vsig in the sub-pixel12 during a period from timing t11 to timing t12 (a writing period P11).More specifically, first, the power line drive section 26 may supply thevoltage Vccp to the source of the drive transistor DRTrP ((D) of FIG.36). Then, the data line drive section 27 may set the signal Sig to thepixel voltage Vsig at timing t11 ((B) of FIG. 36), and the scan linedrive section 23 may change the voltage of the scan signal WS from lowlevel to high level ((A) of FIG. 36). As a result, the write transistorWSTr may be put into ON state, and the gate voltage Vg of the drivetransistor DRTr may be set to the voltage Vsig ((C) of FIG. 36). Thelight emitting element 30 may emit light in this way during a periodsubsequent to timing t11 (emission period P12).

Also, for example, in the embodiments and other examples describedabove, the sub-pixel has a so-called “2Tr1C” configuration; however, theconfiguration is not limited thereto, and other element may be added toconfigure the sub-pixel. Specifically, for example, as with a sub-pixel11A illustrated in FIG. 37, a power transistor DSTr controlling supplyof the power signal DS to the drive transistor DRTr may be provided toform a so-called “3Tr1C” configuration.

Also, for example, in the embodiments and other examples describedabove, the so-called top-emission light emitting element 30 is used;however, the light emitting element is not limited thereto.Alternatively, for example, a so-called bottom-emission light emittingelement in which light emitted from the light emitting layer 230 travelstoward the transparent substrate 200 serving as the support substratemay be used. Moreover, in this case, unlike the top-emission type, thetransparent substrate 200 may be formed of a substrate havingtransparency because the transparent substrate 200 is provided on asurface from which the light is emitted.

Further, for example, in the embodiments and other examples describedabove, the display device has the organic EL element; however, thedisplay device is not limited thereto. Any other display device may beused as long as the display device includes a current-driven displayelement.

Moreover, examples of the method of lengthening the channel CH of thedrive transistor DRTr may include those illustrated in FIGS. 38A to 38D.In reference examples illustrated in FIGS. 38A and 38B, the polysilicon203 is folded in the middle of the region where the gate 201 isprovided. More specifically, in the drive transistor DRTr (FIG. 7 andFIG. 10) according to the above-described embodiments, the polysilicon203 is folded in the region where the gate 201 is not provided, whereasin the drive transistor DRTr (FIGS. 38A and 38B) according to thisreference example, the polysilicon 203 is folded in the region where thegate 201 is provided. In a reference example illustrated in FIG. 38C,the polysilicon 203 is bent by 90 degrees in the middle of the regionwhere the gate 201 is provided. In a reference example illustrated inFIG. 38D, the polysilicon 203 is bent left by 90 degrees and then bentright by 90 degrees in the middle of the region where the gate 201 isprovided.

Moreover, the effects described in the present specification areillustrative and non-limiting. Effects achieved by the technology may beeffects other than those described above.

Moreover, the technology may be configured as follows.

(1) A display device including:

a light emitting element; and

a drive transistor including a coupling section and a plurality ofchannel sections coupled in series through the coupling section, whereinthe drive transistor is configured to supply a drive current to thelight emitting element.

(2) The display device according to (1), wherein each of the pluralityof channel sections extends in a first direction.

(3) The display device according to (2), wherein

the plurality of channel sections are provided in a same layer, and

the coupling section is provided in a same layer as the layer where theplurality of channel sections are provided.

(4) The display device according to (3), wherein the plurality ofchannel sections are juxtaposed along a second direction.

(5) The display device according to (2), wherein the plurality ofchannel sections are provided in different layers from one another.

(6) The display device according to (5), wherein

the drive transistor includes a first gate electrode and a second gateelectrode,

the plurality of channel sections include a first channel section and asecond channel section, and

the first gate electrode, the first channel section, the second gateelectrode, and the second channel section are laminated in this orderwith an insulating layer in between.

(7) The display device according to (5), wherein

the drive transistor includes a first gate electrode and a second gateelectrode,

the plurality of channel sections include a first channel section and asecond channel section, and

the first gate electrode, the first channel section, the second channelsection, and the second gate electrode are laminated in this order withan insulating layer in between.

(8) The display device according to (5), wherein

the drive transistor includes a gate electrode,

the plurality of channel sections include a first channel section and asecond channel section, and

the first channel section, the gate electrode, and the second channelsection are laminated in this order with an insulating layer in between.

(9) The display device according to any one of (2) to (8), furtherincluding a plurality of drive transistors, wherein

each of the channel sections of the plurality of drive transistorsextends in the first direction.

(10) The display device according to any one of (1) to (9), furtherincluding a write transistor including a gate electrode and a gateinsulating film, wherein

the drive transistor includes a gate electrode and a gate insulatingfilm,

the write transistor transfers a pixel voltage to the gate electrode ofthe drive transistor, and

the gate insulating film of the drive transistor is thicker than thegate insulating film of the write transistor.

(11) The display device according to (10), wherein the gate insulatingfilm of the drive transistor includes a first insulating layer and asecond insulating layer provided between the first insulating layer andthe gate electrode of the drive transistor.

(12) The display device according to (11), wherein the gate insulatingfilm of the write transistor further includes a third insulating layerformed of a same material as the first insulating layer, on a same layeras the first insulating layer.

(13) The display device according to (12), wherein a dielectric constantof the second insulating layer is smaller than a dielectric constant ofthe first insulating layer and a dielectric constant of the thirdinsulating layer.

(14) The display device according to (11), wherein the gate insulatingfilm of the write transistor includes a fourth insulating layer formedof a same material as the second insulating layer, on a same layer asthe second insulating layer.

(15) The display device according to (14), wherein the gate insulatingfilm of the write transistor further includes a third insulating layerformed of a same material as the first insulating layer, on a same layeras the first insulating layer, wherein the third insulating layer has athickness smaller than a thickness of the first insulating layer.

(16) The display device according to (14) or (15), wherein a dielectricconstant of the first insulating layer is smaller than a dielectricconstant of the second insulating layer and a dielectric constant of thefourth insulating layer.

(17) The display device according to any one of (1) to (4), wherein

the plurality of channel sections are formed in a same layer,

the drive transistor includes a gate electrode and anelectrically-conductive layer, and

the electrically-conductive layer, the plurality of channel sections,and the gate electrode are laminated in this order on a substrate withan insulating layer in between.

(18) The display device according to (17), further including a pluralityof drive transistors, wherein

an electrically-conductive layer of one of the plurality of drivetransistors is coupled to an electrically-conductive layer of another ofthe plurality of drive transistors.

(19) The display device according to (17) or (18), wherein theelectrically-conductive layer is supplied with a predetermineddirect-current potential.

(20) The display device according to any one of (1) to (19), furtherincluding a write transistor including one or a plurality of channelsections each formed of poly crystal, wherein

the plurality of channel sections of the drive transistor are formed ofpoly crystal, and

an average size of crystal grains in each of the channel sections of thedrive transistor is smaller than an average size of crystal grains ineach of the channel sections of the write transistor.

(21) The display device according to any one of (1) to (19), furtherincluding a write transistor including one or a plurality of channelsections each formed of poly crystal, wherein

the plurality of channel sections of the drive transistor are formed ofpoly crystal, and

an average size of crystal grains in each of the channel sections of thedrive transistor is substantially equal to an average size of crystalgrains in each of the channel sections of the write transistor.

(22) The display device according to (20) or (21), further including adrive section including a plurality of transistors, each of thetransistors including a channel section formed of polycrystal, wherein

the light emitting element, the drive transistor, and the writetransistor constitute a unit pixel, and

the drive section drives the unit pixel, wherein

an average size of crystal grains in each of the channel sections of thedrive transistor is smaller than an average size of crystal grains inthe channel section of each of the transistors of the drive section.

(23) A method of manufacturing a display device, the method including:

forming a drive transistor and a write transistor, the drive transistorincluding a coupling section and a plurality of channel sections coupledin series through the coupling section, and the write transistorconfigured to transfer a pixel voltage to a gate electrode of the drivetransistor; and

forming a light emitting element supplied with a current by the drivetransistor.

(24) The method of manufacturing the display device according to (23),wherein, when forming a gate insulating film of the drive transistor andthe write transistor, a first insulating layer and a second insulatinglayer are formed in this order in a region where the drive transistorand the write transistor are to be formed, and the second insulatinglayer is removed thereafter from the region where the write transistoris to be formed.

(25) The method of manufacturing the display device according to (23),wherein, when forming a gate insulating film and the gate electrode ofthe drive transistor and a gate insulating film and a gate electrode ofthe write transistor,

a first insulating layer is formed in a region where the drivetransistor and the write transistor are to be formed,

the gate electrode is then formed in the region where the writetransistor is to be formed,

a second insulating layer is then formed in the region where the drivetransistor and the write transistor are to be formed, and

the gate electrode is then formed in the region where the drivetransistor is to be formed.

(26) The method of manufacturing the display device according to (23),wherein, when forming a gate insulating film of the drive transistor andthe write transistor,

a first insulating layer is formed in a region where the drivetransistor and the write transistor are to be formed,

a portion or all of the first insulating layer is then removed from theregion where the write transistor is to be formed, and

a second insulating layer is then formed in each of the region where thedrive transistor and the write transistor are to be formed.

(27) The method of manufacturing the display device according to any oneof (24) to (26), wherein one or both of the first insulating layer andthe second insulating layer comprise a plurality of insulating layers.

(28) An electronic apparatus provided with a display device and acontrol section configured to control operation of the display device,the display device including:

a light emitting element; and

a drive transistor including a coupling section and a plurality ofchannel sections coupled in series through the coupling section, whereinthe drive transistor is configured to supply a drive current to thelight emitting element.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations, and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

The invention claimed is:
 1. A display device comprising: a plurality ofpixels, one pixel of the plurality of pixels including: a light emittingelement; a capacitor; a write transistor configured to supply a datasignal from a data signal line to the capacitor in response to a controlsignal supplied through a control signal line that extends in a firstdirection; and a drive transistor configured to supply a drive currentto the light emitting element in response to voltage stored in thecapacitor, wherein the drive transistor includes: a first channel, afirst drain arranged in a second direction that is different from thefirst direction, a first gate that extends in the first direction, and afirst source arranged in the second direction, wherein the writetransistor includes: a second channel, a second gate, a second drain,and a second source, wherein, in a region where the write transistor isdisposed, a first insulating layer, the second channel, a secondinsulating layer, and the second gate are stacked on a substrate in thisorder, and wherein, in a region where the drive transistor is disposed,an electrically-conductive layer, the first insulating layer, the firstchannel, the second insulating layer, and the first gate are stacked onthe substrate in this order.
 2. The display device of claim 1, whereinthe second drain and the second source are arranged in the seconddirection.
 3. The display device of claim 1, wherein the first channelis a part of a first silicon layer including a plurality of recessportions.
 4. The display device of claim 3, wherein the drive transistorfurther includes: one or more contacts; and the electrically-conductivelayer that is arranged in a region including the first gate, at leastone of the plurality of recess portions, and at least one contact of theone or more contacts.
 5. A display device comprising: a plurality ofpixels, one pixel of the plurality of pixels including: a light emittingelement; a capacitor; a write transistor configured to supply a datasignal from a data signal line to the capacitor in response to a controlsignal supplied through a control signal line that extends in a firstdirection; and a drive transistor configured to supply a drive currentto the light emitting element in response to voltage stored in thecapacitor, wherein the drive transistor includes: a first channel, afirst drain, a first gate, and a first source, wherein the writetransistor includes: a second gate, a second drain, and a second source,and wherein the second drain and the second source are arranged in asecond direction that is different from the first direction, whereinadditional pixels of the plurality of pixels individually include asecond light emitting element; a second capacitor; a second writetransistor configured to supply a second data signal from the datasignal line to the second capacitor in response to a second controlsignal supplied through the control signal line that extends in thefirst direction; and a second drive transistor configured to supply asecond drive current to the second light emitting element in response tovoltage stored in the second capacitor, wherein the second drivetransistor includes: a third channel, a third drain, a third gate, and athird source, wherein the second write transistor includes: a fourthgate, a fourth drain, and a fourth source, wherein the fourth drain andthe fourth source are arranged in the second direction that is differentfrom the first direction, and wherein the additional pixels are distinctfrom the one pixel.
 6. The display device of claim 5, wherein the thirddrain and the third source are arranged in the second direction.
 7. Thedisplay device of claim 5, wherein the additional pixels of theplurality of pixels individually include a second silicon layer having asecond recess portion, wherein the third channel is part of the secondsilicon layer.
 8. The display device of claim 7, wherein the seconddrive transistor further includes one or more second contacts; and asecond electrically-conductive layer that is arranged in a regionincluding the third gate, the second recess portion, and the one or moresecond contacts.
 9. The display device of claim 8, wherein theadditional pixels of the plurality of pixels individually include: athird insulating layer, and a fourth insulating layer, wherein, in asecond region where the second drive transistor is disposed, the secondelectrically-conductive layer, the third insulating layer, the thirdchannel, the fourth insulating layer, and the third gate are stacked ona substrate in this order.
 10. The display device of claim 3, whereinthe second channel is a part of a second silicon layer.
 11. The displaydevice of claim 10, wherein the first silicon layer and the secondsilicon layer are distinct from each other.
 12. The display device ofclaim 1, wherein in the region where the write transistor is disposed,any electrically-conductive layer is not arranged between the substrateand the first insulating layer.
 13. The display device of claim 4,wherein the one or more contacts includes a first contact and a secondcontact respectively connected to the first silicon layer, and whereinthe first channel is arranged within a path between the first contactand the second contact.
 14. The display device of claim 13, wherein thefirst contact is electrically connected to a power line, and wherein thesecond contact is electrically connected to an anode of the lightemitting element.